The present invention relates to tank pressure control systems, and particularly to an apparatus for regulating discharge of liquid fuel and fuel vapor from a fuel tank. More particularly, the present invention relates to a tank venting control valve assembly that closes automatically to prevent discharge of agitated liquid fuel from the tank or block overfilling of the tank and opens automatically after agitation of liquid fuel in the tank has subsided or refueling has been completed causing the fuel level in the tank to fall.
New fuel vapors are generated in vehicle fuel tanks during refueling due to splash and agitation of the dispensed fuel, as well as from potential temperature differences between the fuel tank and the dispensed fuel. In addition, as the liquid fuel dispensed at the pump fills the vehicle fuel tank, fuel vapors that are present in the tank and generated during refueling are displaced by liquid fuel. These displaced fuel vapors are moved out of the fuel tank vapor space by the displacing action of the liquid fuel.
In many conventional vehicle fuel systems, these displaced vapors are released directly into the atmosphere via the fuel tank filler neck and are a contributing factor to air pollution. In other vehicle fuel systems, these displaced vapors are exhausted from the fuel tank by a venting valve to a vapor recovery canister designed to capture and store fuel vapors that are displaced and generated in a fuel tank during a typical vehicle refueling operation. On-board fuel vapor recovery systems are disclosed, for example, in U S. Pat. Nos. 4,770,677; 4,816,045; and 4,836,835.
One shortcoming of typical conventional tank venting valves is that the discharge capacity of the valve is lower than that capacity necessary to vent the fuel tank properly during refueling because of small size requirements imposed on these valves. Such small size requirements are made necessary by the shortage of available space in the vicinity of the vehicle fuel tank. Inadequate discharge capacity can result in unwanted discharge of fuel vapor to the atmosphere if fuel vapor exits the tank through the filler neck or other outlet because the conventional tank pressure control valve is unable to regulate the discharge of pressurized fuel vapor to a canister or other suitable fuel vapor treatment site properly and in a timely manner.
One object of the present invention is to provide a tank pressure control valve of small size and economical construction that nevertheless is configured to discharge a substantial volume and mass of pressurized fuel vapor from a fuel tank using a minimum of moving parts during development of high vapor pressure in the tank such as occurs during refueling or the like.
Another object of the present invention is to provide a tank venting control valve assembly that automatically closes a tank venting outlet at a predetermined fuel level during tank refueling operations to prevent a fuel pump operator from overfilling the tank.
Yet another object of the present invention is to provide a valve assembly that automatically closes the tank venting outlet whenever fuel sloshes around in a vehicle fuel tank as a result of vehicle movement to prevent fuel carryover from the fuel tank through the tank venting outlet to a vapor recovery canister.
Still another object of the present invention is to provide a valve assembly that closes the tank venting outlet during fuel sloshing as required to prevent fuel carryover to the vapor recovery canister and reopens the tank venting outlet after fuel sloshing has ended or after the pressure of fuel vapor in the tank has risen to a predetermined high level.
Yet another object of the present invention is to provide a valve assembly that closes the tank venting outlet during vehicle rollover.
According to the present invention, an apparatus is provided for regulating discharge of liquid fuel and fuel vapor from a fuel tank. The apparatus includes a vent assembly couPled to the fuel tank and a first nipple movable relative to the vent assembly. The vent assembly is formed to include a venting outlet aperture. The first nipple includes a first tip configured to close the venting outlet aperture upon engagement of the first tip and the vent assembly.
The first nipple is also formed to include a bypass passageway extending therethrough to conduct fuel vapor from the fuel tank to the venting outlet aperture through an outlet opening formed in the first tip. The apparatus further includes a second nipple movable relative to each of the vent assembly and the first nipple. The second nipple includes a second tip configured to close the bypass passageway formed in the first nipple upon engagement of the first and second nipples. The first and second nipples cooperate to close the venting outlet aperture formed in the vent assembly upon movement of the first and second nipples relative to the vent assembly to predetermined closure positions so that fuel vapor in the tank is blocked from venting through the vent assembly.
The apparatus further includes means for moving the second nipple relative to the vent assembly to cause the second tip to engage the first nipple and move it upwardly to engage the vent assembly and close the venting outlet aperture. At the same time, the second tip mates with the first nipple to close the bypass passageway. The second nipple is moved by the moving means in response to rising levels of liquid fuel in the fuel tank so that liquid fuel is unable to escape from the fuel tank through the venting outlet aperture.
The moving means includes a float member buoyantly supported on liquid fuel in the fuel tank and the second nipple is coupled to the float member for movement therewith. The second tip is situated to move with the float member in an upward direction toward the first nipple as the level of liquid fuel rises in the fuel tank and in a downward direction away from the first nipple as the level of liquid fuel falls in the fuel tank.
It will be understood that the level of fuel could rise in a fuel tank, for example, either during sloshing or other agitation of fuel in the tank as might occur during vehicle movement or cornering, or during filling the tank with fuel during refueling. Of course, the level of fuel in a fuel tank could fall whenever fuel sloshing or agitation ends or as fuel is pumped out of the tank and used in the vehicle engine. The float member (and the second nipple appended thereto) will move in an upward direction in the tank whenever the fuel level therein rises and in a downward "sinking" direction whenever the fuel level therein falls.
In operation, the buoyant float member will move around in the fuel tank, for example, as liquid fuel is sloshed around in the tank or introduced into the tank, to move the first and second nipples upwardly in the manner described above to close the venting outlet aperture formed in the vent assembly. Advantageously, such blockage of the venting outlet aperture is effective to prevent liquid fuel carryover from the fuel tank to a fuel vapor recovery canister connected to the fuel tank through the vent assembly.
Further, the first and second nipples move in sequence to reopen the venting outlet aperture quickly whenever the float member sinks because fuel sloshing ends or the fuel level in the fuel tank decreases and risk of liquid fuel carryover to the vapor recovery canister is lessened. Such reopening of the venting outlet aperture allows pressurized fuel vapor in the fuel tank once again to vent freely from the tank to the vapor recovery canister at a maximum rate.
The venting outlet aperture is reopened typically in the following manner. As the float member sinks, the second nipple moves downwardly away from the first nipple causing the second tip to move away from its position closing the bypass passageway. Following such downward movement of the second nipple, pressurized fuel vapor can once again be vented from the fuel tank through the bypass passageway formed in the first nipple even while the first nipple remains in its closed position, closing the venting outlet aperture.
Advantageously, such venting through the bypass passageway will expose the first tip of the first nipple to pressurized fuel vapor from the tank and this pressurized fuel vapor will bear against the first tip to apply a downward force to the first nipple which will assist in positively moving the first nipple away from its closed position to an opened position allowing maximum venting of fuel vapor through the venting outlet aperture in the vent assembly. The apparatus also includes flange means that is arranged to move with the float member so that it engages arm means appended to the first nipple as the float member sinks in the fuel tank in response to falling levels of liquid fuel therein so that the first nipple is moved downward relative to the vent assembly by the float member to cause the first tip of the first nipple to disengage the vent assembly, thereby opening the venting outlet aperture.
Additional objects, features, and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of preferred embodiments exemplifying the best mode of carrying out the invention as presently perceived.